Grayson used words like “incredible” and “bizarre” after Saints tore European rugby’s form book to shreds to stun quarter-final opponents Biarritz 7-6 – after Robbie Kydd’s interception try was converted by Carlos Spencer – to set up a first all-English Heineken Cup semi-final since 2001 against Wasps.

Saints are currently bottom of the Guinness Premiership with only three games remaining, but Grayson added: “The Premiership will be what the Premiership will be. Right now, the players deserve 24 hours to bask in the glory of a pretty incredible victory. We have made the Heineken Cup semi-finals against all the odds.”

He added: “It proves that on any given day, sport can turn up some bizarre results.”

The April 22 tie against Wasps, at Coventry City’s 32,000-capacity Ricoh Arena, is a repeat of the 2000 quarter-final clash between the clubs. Grayson kicked 20 points on that occasion as Saints triumphed 25-22 and then went on to lift the trophy by defeating Munster at Twickenham.

Grayson added: “I think we were 100-1 in a two-horse race, but that’s what sport is all about. In the big picture, we didn’t really think about getting a win because on paper, Biarritz should realistically have won.

“We wanted to frustrate them and keep the score close, because you never know when you are going to get something like an intercept to turn the game.”

A shell-shock Biarritz coach Patrice Lagisquet said: “I am disappointed, angry and frustrated. Going into the game, no way could I see Northampton beating us.

“At half-time, I said we had to be patient and put away our chances, but we didn’t do it. I would be extremely surprised if Northampton beat Wasps in the semi-final.”